High energy x-ray tubes are used in medical device applications to provide an x-ray source. The materials in the x-ray tube are subject to high temperatures during the operation of the x-ray tube. The x-rays generated by the x-ray tube are directed out of a window toward a target such as portion of a patient. The x-ray tube is subject to high temperatures when the x-ray tube is generating x-rays and then cools. A heat shield may be secured to a portion of the x-ray tube to shield the window from backscattered electrons.